I tried on my Onyx Boox. E.g. the Russian and Dutch lines do not display correctly, but I can read Dutch and Russian books on my device without any problem, and without installing fonts. But then my Russian books are in fb2 format.

This looks like an ADE issue rather than an issue with the Onyx Boox. When I open the epub in ADE on the PC, I have the same display problems.

Any reader that supports ADE can show any language out of the box. You just have to embed the needed fonts into the ePub and you are good to read.

That's only partly true. The table of contents uses the default font of the device, not the embedded font. Try to read a Russian or a Japanese ePub-book in your PRS 505. The table of contents will look as follows:

That's only partly true. The table of contents uses the default font of the device, not the embedded font. Try to read a Russian or a Japanese ePub-book in your PRS 505. The table of contents will look as follows:

- ???? ???? ??? ??? ??? ???
- ??? ??? ???? ????? ???? ???

Not very handy.

So put in an internal ToC and have the external ToC link to the internal ToC.

It surely is an ADE issue. ADE only displays a small subset of Unicode characters by default.

I could also rephrase my question: is there somewhere a list of devices that do not use ADE's engine?

If they support Adobe DRM, then they are using the ADE SDK.

FBReader does not provide full ePub support, but it is often "good enough" and it does allow the use of any font installed on the device and that font is used for everything (i.e. for TOCs). It also supports right to left languages (I think, but I have never tested this). Devices with FBReader out of the box include the PocketBooks, the Onyx Boox 60/Bookeen Neo and the Azbooka N516. The Azbooka is for DRM-free ebooks only. The Onyx and PocketBooks use ADE for ePubs, but the PocketBooks have the option of switching to FBReader for DRM-free ePubs.

OpenInkPot is the native firmware on the Azbooka, and can be added by the owner to a Hanvon N516 and a Hanlin V3. It is also possible to add FBReader to the V3's standard firmware. It can be added as 3rd party software to all the iLiad devices.

Finally, it is entirely possible for any Reader vendor to replace Adobe's default font in mobile Adobe Digital Editions. Jinke has done this to support Asian languages on the Hanlins, and Bookeen allows the user to select the default font (I don't know how good the language coverage is in their built-in fonts though). I assume that any Reader vendor could also fix the "TOC in another font" bug too, although this is more appropriately an Adobe issue.